This invention relates to resilient propeller hub assemblies capable of transmitting torque from a propeller drive shaft to a marine propeller and absorbing torque shock in the event that the propeller inadvertently strikes underwater objects. More particularly, the invention relates to a progressive shear assembly typically including multiple shear rods of the same or various hardness and resilience and which can be interposed between a propeller drive shaft and a marine propeller in selected combinations, ratios and sequences and in such a manner that a selected resilience and torsional resistance of the propeller with respect to the drive shaft is achieved for different applications of the propeller. Typically, a rod seat is defined between adjacent ones of multiple torsion ribs provided in spaced-apart relationship to each other in the propeller hub. An adaptor shaft, provided with one or more drive ribs that interface with the respective torsion ribs in the propeller hub, engages the drive shaft for rotation therewith. Multiple shear rods are provided in each of the rod seats, and the shear rods in each rod seat can be of the same or different materials of construction and resilience to achieve a selected balance of torque resistance and resilience of the propeller with respect to the drive shaft in the event that the propeller strikes a submerged object. In that event, as rotation of the propeller suddenly stops or slows and the drive shaft continues to rotate, the shear rods are compressed between a corresponding one of the drive ribs on the adaptor shaft and the corresponding torsion rib in the propeller hub, and the resultant torque shock is absorbed by the shear rods. Accordingly, the shear rods tend to deform and shear and prevent or minimize damage to the propeller and propeller drive train components, and can be easily and inexpensively replaced. Some of the shear rods typically remain intact to facilitate continued structural integrity and drive capability between the drive shaft and the propeller and continued operation of the propeller. In another embodiment, a torsion sleeve is provided in the propeller hub and a drive sleeve, mounted on the propeller drive shaft, extends into the torsion sleeve. Multiple shear rods are interposed between a pair of torsion ribs provided on the torsion sleeve and a pair of drive ribs that extend from the drive sleeve and interface with the torsion ribs.
While past techniques for securing propellers to propeller drive shafts include welding, pinning or splining, excessive torque loading or shock applied to the drive shaft, gears and other propeller drive train components has a tendency to damage the components in the event that the rotating propeller strikes a submerged obstacle. Consequently, repairing the propeller, drive shaft, gears or other propeller drive train components can be expensive and time-consuming. Various patents of interest in this regard include U.S. Pat. Nos. 2,363,469; 2,539,630; 2,869,774; 2,993,544; 3,045,763; 3,096,106; 3,136,370; 3,256,939; 3,307,634; 3,318,388; 3,407,882; 3,563,670; 3,701,611; 3,748,061; 4,338,064; 4,452,591; 4,566,855; 4,575,310; 4,826,404; 4,842,483; 5,049,034; 5,201,679; 5,322,416; 5,484,264; and 5,522,743.
An object of this invention is to provide a progressive shear assembly which is capable of preventing damage to a marine propeller or various components of the propeller drive train during operating load periods and in the event that the propeller strikes an underwater obstacle.
Another object of this invention is to provide a progressive shear assembly suitably adapted for propellers, including multiple rods of selected shape and uniform or various hardness and resiliency which absorb torque shock in the event that a marine propeller strikes a submerged object to prevent damage to the propeller and/or drive shaft, gears or other propeller drive train components.
Still another object of the invention is to provide a progressive shear assembly for propellers, including multiple shear rods or cylinders of selected composition, resiliency, configuration and length and which can be arranged in selected combinations and sequences with respect to each other to impart a selected longitudinal cushioning effect as well as torque resistance and torsional resilience between a marine propeller and a drive shaft for the propeller.
Yet another object of this invention is to provide a progressive shear assembly for marine propellers, including multiple shear rods or cylinders of selected cross-sectional configuration, length, hardness and resiliency and at least some of which shear rods or cylinders are air or gas-filled, for absorbing torque shock during operating loads and in the event that the propeller inadvertently strikes a submerged obstacle, which shear rods or cylinders can be easily and inexpensively replaced.
A still further object of this invention is to provide a progressive shear assembly capable of connecting a marine propeller to a propeller drive shaft attached to a boat motor, which progressive shear assembly includes multiple shear rods or cylinders of selected composition, resilience, length and configuration, some of which shear rods are sheared to absorb torque shock during power surges and in the event that the rotating propeller strikes an underwater obstacle and others of which shear rods or cylinders may remain intact to provide continued drive capability between the drive shaft and the propeller and facilitate continued operation of the propeller and structural integrity of the drive shaft and drive train.
Another object of this invention is to provide a progressive shear assembly including a torsion sleeve provided in a propeller hub; a drive sleeve mounted on the propeller drive shaft and extending into the torsion sleeve; multiple shear rods or cylinders interposed between a pair of torsion ribs provided on the torsion sleeve; and a pair of drive ribs that extend from the drive sleeve and interface with the torsion ribs.
These and other objects of the invention are provided in a progressive shear assembly typically including multiple solid or gas-filled shear rods or cylinders of similar or various resilience, composition and length and which can be interposed between a propeller hub of a marine propeller and a propeller drive shaft in selected lengths, cross-sectional configurations, combinations, ratios and sequences in such a manner that a desired balance of resilience and torsional, as well as longitudinal resistance of the propeller hub with respect to the drive shaft is achieved for different applications of the propeller. Typically, a rod seat is defined between adjacent ones of multiple torsion ribs provided in spaced-apart relationship to each other in the propeller hub. An adaptor shaft, provided with multiple drive ribs that interface with the respective torsion ribs in the propeller hub, engages the propeller drive shaft for rotation therewith. Multiple shear rods or cylinders are provided in each of the rod seats, and the shear rods or cylinders in each rod seat can all be the same composition and resilience or any combination and sequence of shear rods or cylinders having different compositions and resilience to achieve a selected balance of torsional and/or longitudinal resistance and resilience of the propeller with respect to the drive shaft during power surges and in the event that the propeller strikes a submerged object and suddenly slows or stops rotation. In that event, the shear rods or cylinders are compressed and one or more of the rods or cylinders sheared between a corresponding one of the drive ribs on the adaptor shaft and the corresponding torsion rib in the propeller hub as the torque shock imparted by the still-rotating drive shaft is absorbed by the shear rods or cylinders. Accordingly, the shear rods or cylinders tend to deform and shear and prevent damage to the propeller or the drive shaft, gears or other propeller drive train components, and can be easily and inexpensively replaced. Some of the shear rods or cylinders typically remain intact to facilitate continued structural integrity and drive capability between the motor drive shaft and the propeller and continued operation of the propeller. In another embodiment, a torsion sleeve is provided in the propeller hub and a drive sleeve, mounted on the propeller drive shaft, extends into the torsion sleeve. Multiple shear rods or cylinders are interposed between a pair of torsion ribs provided on the torsion sleeve and a pair of drive ribs that extend from the drive sleeve and interface with the torsion ribs.